Problem: Simplify the following expression: $ p = \dfrac{-8n + 9}{7n} - 9 $
Explanation: In order to subtract expressions, they must have a common denominator. Multiply the second expression by $\dfrac{7n}{7n}$ $ \dfrac{9}{1} \times \dfrac{7n}{7n} = \dfrac{63n}{7n} $ Therefore $ p = \dfrac{-8n + 9}{7n} - \dfrac{63n}{7n} $ Now the expressions have the same denominator we can simply subtract the numerators: $p = \dfrac{-8n + 9 - 63n }{7n} $ Distribute the negative sign: $p = \dfrac{-8n + 9 - 63n}{7n}$ $p = \dfrac{-71n + 9}{7n}$